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CVE-2026-118021

Sandbox escape due to use-after-free in the XPCOM component

CVSS score

—

EPSS probability

—

Risk score

—

Published

4 h ago

OverviewPublic Exploits (0)NewsroomVulnerability Timeline
Patch status has not yet been verified

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Vulnerability description

DayBreach AI Explanation

Verified against sources

CVE-2026-118021: Firefox XPCOM Component Use-After-Free Vulnerability

Sources read

2

Source agreement

Tam uyum

Evidence confidence

%63

Short explanation

A sandbox escape vulnerability due to a use-after-free flaw in the XPCOM component has been reported in Mozilla Firefox [S0]. The vulnerability was addressed in Firefox 159 [S0].

Why does it matter?

Sandbox escape vulnerabilities are critical as they can allow attackers to bypass security boundaries and gain elevated capabilities within the environment [S0].

What should be done?

  • Upgrade Firefox to the recommended vendor versions [S0]
  • Review the vendor security advisories for updates [S0]
Chain of evidence and sources2 verified claims

CVE-2026-118021, XPCOM bileşenindeki use-after-free hatasından kaynaklanan bir koruma alanı dışına çıkma açığıdır.

S0 · daybreach-canonicalS1 · cvelist

İlgili zafiyet Firefox 159 sürümünde giderilmiştir.

S0 · daybreach-canonicalS2 · nvd
Show the technical text from the sources

Sandbox escape due to use-after-free in the XPCOM component. This vulnerability was fixed in Firefox 159 and Thunderbird 159.

This explanation was compiled automatically from the source records. Scores, active exploitation, patch and exploit status come straight from the sources.

IMPACT: Affected Products and Software

Affected Products

The following products are affected by CVE-2026-118021 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.

IDVENDORPRODUCTACTION
1mozillafirefox View
2mozillathunderbird View
Total affected vendors: 1|Products: 2

RED HAT CSAF/VEX: Product Impact Check

Red Hat has not yet published a CSAF/VEX impact record for this CVE. This does not mean “not affected”.

SCORING: CVSS from Multiple Sources

CVSS Scores

The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.

SCOREVERSIONSEVERITYVECTORSOURCE
The sources have not yet published a verified CVSS metric.

Patch and Remediation Guide

Solution & Remediation Advisory

Patch status unknown

İncelenen resmî kaynaklarda yama durumu doğrulanamadı. Bu sonuç “yama yok” anlamına gelmez.

Confirm the affected product and version against the source evidence above.
Restrict access to internet-facing services and apply network segmentation.
Until a patch is confirmed, follow the vendor advisory; do not read an unknown status as “no patch”.
Monitor server logs and network endpoints for signs of anomalous execution.

Public exploit and active exploitation status

Verified exploit intelligence

No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.

Weakness Classification and Attack Patterns (CWE & CAPEC)

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-118021 is associated with the following CWEs:

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')CWE-20: Improper Input Validation

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-118021 weaknesses.

CAPEC-66: SQL InjectionCAPEC-126: Path TraversalCAPEC-28: OS Command Injection

Official Sources and Advisories

https://bugzilla.mozilla.org/show_bug.cgi?id=2076695vendor-advisoryhttps://www.mozilla.org/security/advisories/mfsa2026-118/vendor-advisoryhttps://www.mozilla.org/security/advisories/mfsa2026-121/vendor-advisory

Yama durumu bilinmiyor

İncelenen resmî kaynaklarda yama durumu doğrulanamadı. Bu sonuç “yama yok” anlamına gelmez.

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CVE-2026-118021 · Sandbox escape due to use-after-free in…